Guiding system for an externally actuating of a closing unit

ABSTRACT

The invention relates to a guide system for an externally operated part of a closing unit, in particular for a mold holder of a closing unit, wherein the closing unit ( 12 ) executes during operation a movement in a predefined direction (D), and the externally operated part ( 14 ) is moveable during the course of movement between at least two positions. The externally operated part ( 14 ) includes a guide element embodied in the form of a cam roller ( 24 ) which rolls on a support structure ( 26 - 40 ) for attaining at least one of the positions during the movement of the closing unit ( 12 ). In order to avoid excessive wear and ease a maintenance service, at least one section ( 30 ) of the support structure ( 26 - 40 ) is provided with at least one freely movable support roller ( 40 ) whose respective axis is substantially tangential in relation to the movement direction (D) of the closing unit ( 12 ) so that the cam roller ( 24 ) of the externally operated part ( 14 ) rolls substantially without sliding friction on the support roller ( 40 ).

The invention relates to a guide system for an externally operated partof a closing unit, in particular for tool holders of a closing unit,according to the preamble of claim 1.

In the following, reference is made to a closing unit for a plasticsprocessing machine with at least one tool holder in which a tool, alsocalled mold or half-mold, is held. It should be expressly noted,however, that the present invention is equally applicable for otherexternally operated parts of closing units.

Closing units of plastics processing machines, such as polyurethaneinstallations, normally have two mold holders which are movable forclosing and opening of the closing unit and thus at the same time of theaccommodated mold. In this context, reference is made to German patentpublication DE 101 52 392 which describes a closing unit for a plasticsmachine. The illustrated closing unit includes a lower mold holder andan upper mold holder which are each swingable about a common axis.During operation of the entire closing unit, the lower mold holder ismoved back and forth between two positions, namely a lower position inwhich the mold elements are placed into a mold or mold parts can beremoved, and an upper position in which the starting material isintroduced and the closing unit overall is closed to allow reaction ofthe foam components.

In DE 101 52 392, the closing units themselves are fixedly disposed atone location, only the mold holders are swingably mounted.

It is, however, known, to arrange for example several closing units upona rotary platform, with the individual closing units successivelyundergoing the same operating steps during operation of the rotaryplatform. For example, a starting material may be introduced, when theclosing unit is open. At the same time, the reaction takes place inother closing units. In still another closing unit, a finished moldedpart may be withdrawn at the same time. The use of such devices—likewiseas in DE 101 52 392—requires operation, especially pivoting, of thevarious parts of the closing unit in a predefined manner.

A method for external operation of a mold holder is know per se, using aguiding slot mechanism, whereby a cam roller is arranged upon anexternally operated (i.e. from outside the closing unit) part of aclosing unit, for example the lower mold holder, for running on asupport structure. Conventionally, the support structure is realized bya rail arrangement whose respective height is so constructed via forexample a rotation section of the rotary platform that the pivotingposition of the cam roller mounted to the part being externally actuatedcan be adjusted as the cam roller is supported and rolls off.Concretely, the support structure includes, for example, two rampportions, namely an upwardly directed ramp and a downwardly directedramp as well as a rail part at constant height disposed in-between. Whenthe cam roller of the part to be externally operated reaches theupwardly directed ramp, this part of the closing unit is, for example,elevated to an upper position as the cam roller rolls on this supportsection, and remains there for as long as the cam roller rolls on thefurther rail section at constant height. When the cam roller then rollsfinally along the downwardly directed ramp, the part to be externallyoperated is moved by its own weight downwards and ultimately brought toa standstill in a predefined position by a stop.

The use of such rigid rails for a support structure suffers, however,the drawback of experiencing substantial wear as a result of frictionwhen imprecise adjustment causes a relative movement between cam rollerand rail. Moreover, the precise manufacture of such rail system hasproven expensive and complicated. Complex is also the replacement ofcertain rail portions.

It is an object of the present invention to minimize in a guide systemof the afore-stated type the wear at least on some partial sections andto ensure easy replacement.

This object is attained by the features set forth in claim 1.

An essential feature of the invention is thus the provision of at leastone section of the support structure with a freely moveable supportroller having an axis in substantial parallel or tangential relationshipto the movement direction of the closing unit or cam roller on theclosing unit. As a consequence of this constructive design, there is nosliding friction, even when the point of contact of the cam roller onthe support structure shifts because the support roller is turned in therespective manner during such shift of the point of contact and the camroller rolls thereby in its axial direction on the support roller. Inthe absence of a sliding friction, wear on the inventive section of thesupport structure can be significantly reduced. Thus, the mold holdercan be operated externally without friction-based wear, even in thepresence of misalignments and radial deviations of the supportstructure.

Furthermore, the cam roller of the part to be externally operated isacted upon not only in one point or line. Rather, the line of contacttravels across a significant portion of the roller width. Also thesupport rollers of the support structure can travel about the entirecircumference according to a statistical distribution. In contrastthereto, a rigid pipe would always have only one line of contact withthe cam roller.

Overall, minimal wear can be ensured without additional adjustments byan automatic adjustment of the rolling behavior, compensation ofmanufacturing and assembly tolerances, and simplified exchange ofpartial sections of the support structure.

Of course, the section of the support structure, having at least onefreely moveable support roller, may be provided with several supportrollers as well. In this case, the support rollers should overlap intheir axial extension such as to establish a smooth transfer of the camroller from one support roller to the next support roller.

According to a preferred embodiment of the invention, upwardly ordownwardly directed ramps are formed by the sections which include thefreely moveable support rollers. It is these parts of the subassemblythat are subject to stress in particular, on one hand. On the otherhand, precise alignment and construction of these sections requireparticular care when using a rail. When using a support roller inconnection with a ramp, its axis must extend at a certain angle upwardsor downwards in relation to the movement direction so that lifting orlowering of the mold holder becomes possible.

It is not necessarily required to provide the entire support structureby means of support rollers. It is also possible, to realize sections inthe form of the conventional guide rail. In particular, the use of aguide rail is appropriate at such locations that are easy to adjust andless exposed to stress and which encounter anyway little friction-basedwear.

Also, there is no need to continuously define the position of the partto be externally operated through interaction of the cam roller with thesupport structure. It is, for example, possible, to spontaneouslyrealize a lower position of the part to be externally operated byproviding a further frame element of the closing element with a stop forthis part.

According to a particularly preferred embodiment, at least one closingunit is arranged on a turntable. Of course, several closing units (e.g.12 units) may be provided on the turntable at same radial distances fromthe center of the turntable. The turntable can be operated duringoperation of the closing unit so that the individual closing units moveabout a circular line. The roller moves on a toroidal surface line. Whenusing a turntable, the support structure should be arranged about apitch circle and associated to the pivot point. It may includepreferably an upwardly directed ramp which has been realized by means ofthe support rollers, a section with a guide rail, and a downwardlydirected ramp which has also been realized with support rollers.

Of course, the invention may also be used in oval installationsexhibiting a circular or linear movement of the closing units.

An embodiment of the present invention will now de described in greaterdetail by way of example with reference to the attached drawings, inwhich:

FIG. 1 shows a greatly schematic side view of a carousel-typeinstallation with several closing units and a guide system according tothe present invention,

FIG. 2 shows a plan view of a carousel-type system according to FIG. 1,with the carousel shown only partially,

FIG. 3 shows a circular segment of FIG. 2, depicting a detailed view ofa ramp of the guide system according to the invention,

FIG. 4 shows a portion of the schematic illustration according to FIG. 1with the ramp of the guide system according to the invention, and

FIG. 5 shows a portion of a further portion of the carousel of FIG. 1.

The present invention will now be described in greater detail withreference to a carousel-type system for PUR installations (polyurethaneinstallations). However, the invention is not limited to this system.

Several closing units 12 of a PUR installation (2 in FIG. 1, 3 in FIG.2), not shown in more detail, are securely disposed on a turntable 20 atsubstantially same radial distance to its center and in angular offsetrelationship. Each closing unit 12 includes a lower mold holder 14 andan upper mold holder 12 which can both pivot upwardly and downwardlyabout a common joint axis 18. The closing unit can be closed or openedin its entirety by pivoting the lower and upper mold holders 14, 18. Asa consequence, the mold holders can be brought into a position thatallows introduction of mold elements in ergonomically beneficial manneror removal of molded products from the mold.

The present invention is concerned only with pivoting of the lower moldholder 14. The pivot mechanism for the upper mold holder 12 will not bedescribed in more detail.

In relation to the dimension of the turntable, the lower mold holder 14includes a radially outwardly projecting arm having an outer end forarrangement of a cam roller 24. The rotation axis of the cam roller 24substantially coincides with the radial direction of the turntable;however it may also slightly deviate therefrom as a result of theoff-center arrangement.

Each cam roller 24 of a closing unit runs upon a support structure whichin the present case is comprised of two ramps 30 as well as a guide rail26. Both ramps 30 as well as the guide rail 26 extend substantially inthe form of a circular segment over a portion of the outer circumferenceof the turntable 20. The guide rail 26 is held by a plurality ofstanchions 28 of which only one is respectively labeled with a referencecharacter in FIGS. 1 and 2. The guide rail 26 extends—as shown in FIG.1—at constant height.

Provided on each of both ends of the guide rail 26 are two ramps 30,each of which having three stands 32 as shown in greater detail in FIG.3 by the segment 42 cut from FIG. 2. Each stand 32 includes a base 34which is mounted onto the ground radially outside the turntable, asupport leg 36 arranged on the base, an arm 38 disposed on the upper endof the support leg 36, as well as a support roller 40 disposed on theinner end of the arm 38. The support roller 40 is held on both sides inbearings of the arm 38 and freely rotatable about a rotation axis. Therotation axis extends here substantially tangential to the rotationdirection D (see arrow D in FIG. 1) of the turntable 20 and slopesupwardly or downwardly in relation to the rotation movement.

The mode of operation of the turntable is as follows.

The turntable is rotated in direction of arrow D (FIG. 2) together withthe attached closing units 12. When the cam roller 24 of a closing unitreaches the ramp 30, illustrated in FIG. 2 on the left-hand side, itsuccessively runs on the three support rollers 40 upwards. To ensure asmooth rolling operation, the ends of the support rollers 40 overlap inaxial direction so that the cam roller 24, when reaching one end of asupport roller, bears at the same time on a second support roller. Oncethe cam roller 24 of a lower mold holder 14 has passed the supportrollers and has been elevated—together with the mold holder 14- to anupper level, it travels on the rail 26 to the end thereof. Passage ofthe ramp 30 causes the lower mold holder to be elevated from a lowerposition to an upper position. The lower mold holder 14 remains in theupper position so long as the cam roller 24 travels on the rail 26. Whenthe cam roller 24 travels then in opposite manner to the first ramp onthe second ramp shown in FIG. 2 on the right-hand side, the lower moldholder 14 is moved downwards again. In a same manner as in the firstramp, the cam roller 24 runs successively on three support rollers 40 inoverlapping configuration.

The lower position of the mold holder 14 is defined by the frame of themold holder striking against a stop 44. In this position, the cam roller24 has no function.

FIG. 4 depicts again the ramp as formed by the three support rollers 40.The cam roller 24 is hereby not clearly shown. It travels, however,always on one of the support rollers 40.

FIG. 5 illustrates the manner by which the cam roller 24 travels on therail 26 and maintains the lower mold holder in the upper position.

The use of the support rollers 40 in the ramp zone prevents a slidingmovement of the cam rollers 24 on a rail and thus excessive wear.Rather, the support rollers 40 rotate in one or the other direction(substantially in axial direction of the cam roller 24), depending onwhether the contact point travels inwards or outwards to the cam roller24.

In view of the axial change of the contact point upon the cam roller 24,the latter is acted upon not only at one spot. Rather, the line ofcontact travels on the roller width, for example upon 70% of the rollerwidth, thereby also contributing to a minimization of wear.

Thus, there is not necessarily a need to precisely align the individualstands 32 having the support rollers 40 on its upper, inner end in orderto minimize wear as a consequence of sliding friction. In view of thefree rotatability of the support rollers, the sliding friction can beeasily kept small, even when the support rollers are not in precisealignment. Further, the use of several stands with support rollers isconducive for a simple and cost-efficient replacement. Only the onesupport roller has to be replaced which exhibits certain wear after along service life.

Of course, remaining portions of the support structure may also berealized with rollers. However, the guide rail can be manufactured inthe area of constant height with more precise tolerances and with awider running surface so that the use of support rollers is notnecessarily required here.

In summary, the invention allows prevention of excessive wear, easieradjustment, compensation of manufacturing and assembly tolerances, aswell as easier replacement of partial sections. In addition, theinvention also permits an arrangement of the cam roller axes in such away that the touching tangent is prevented from extending through thepivot point of the closing unit.

List of Reference Characters

-   10 Carousel-type system with closing units-   12 closing unit-   14 lower mold holder-   16 upper mold holder-   18 joint axis-   20 turntable-   22 central support with bearing-   24 cam roller of the lower mold holder-   26 rail-   28 rail support-   30 ramp-   32 stand-   34 base-   36 support leg-   38 arm-   40 support roller-   42 segment-   44 stop-   D rotation direction

1. A guide system for an externally operated part of a closing unit,comprising: a support structure; and a closing unit moveable in apredefined movement direction during operation and having an externallyoperated part moveable between at least two positions, said partincluding a guide element in the form of a cam roller which travels onthe support structure for reaching at least one of the positions, as theclosing unit moves, wherein the support structure has at least onesection which includes at least one freely moveable support rollerrotatable about a rotation axis which is arranged in substantialparallel or tangential relationship to the movement direction of theclosing unit so that the cam roller of the externally operated partrolls on the support roller substantially without sliding friction. 2.The guide system according to claim 1, wherein the at least one sectionof the support structure has two or more of said support roller, saidsupport rollers overlapping in their axial extension such as toestablish a smooth transfer of the cam roller from one support roller tothe next support roller.
 3. The guide system according to claim 1,wherein the at least one section forms an upwardly directed ordownwardly directed ramp.
 4. The guide system according to claim 1,wherein the support structure includes a guide rail in overlappingrelationship to the section so as to establish a smooth transfer for thecam roller when moving between the section and the guide rail.
 5. Theguide system according to claim 1, further comprising a stop fordefining a stop position for the externally operated part.
 6. The guidesystem according to claim 1, further comprising a turntable forarrangement of the closing unit, said turntable being constructed tomove the closing unit in a circle during operation of the turntable. 7.The guide system according to claim 6, wherein the section forms a firstramp for upwardly moving the externally operated part, said supportstructure further including a further section to define a second rampfor downwardly moving the externally operated part, and a guide railextending between the first and second ramps, wherein the first andsecond ramps have support rollers or are formed of support rollers. 8.The guide system according to claim 2, wherein one of the sections formsan upwardly directed ramp and another one of the sections forms adownwardly directed ramp.